Device for measuring an activity of lead ions

ABSTRACT

A DEVICE FOR MEASURING AN ACTIVITY OF LEAD IONS COMPRISES A SELECTIVE ELECTRODE AND A REFERENCE ELECTRODE IMMERSED IN A SOLUTION CONTAINING LEAD IONS, SAID SELECTIVE ELECTRODE INCLUDING A DISC IN A BATCH COMPOSITION WHICH COMPRISES A COMBINATION OF LEAD CHALCOGENIDE AND AT LEAST ONE MEMBER SELECTED FROM THE GROUP CONSISTING OF SILVER TELLURIDE AND SILVER SELENIDE OR IN A BATCH COMPOSITION WHICH COMPRISES A COMBINATION OF SILVER SULFIDE AND AT LEAST ONE MEMBER SELECTED FROM THE GROUP CONSISTING OF LEAD TELLURIDE AND LEAD SELENIDE.

APril 23,1974 KENJI HIGASHIYAMA ETAL 3,806,438

DEVICE FOR MEASURING AN ACTIVITY OF LEAD IONS Filed Feb. 28, 1972 United States Patent Oflice 3,806,438 Patented Apr. 23, 1974 3,806,438 DEVICE FOR MEASURING AN ACTIVITY OF LEAD IONS I Kenji Higashiyama and Hiroshi Hirata, Osaka, Japan,

assignors to Matsushita Electric Industrial Co., Ltd., Osaka, Japan Filed Feb. 28, 1972, Ser. No. 229,909 Claims priority, application Japan, Mar. 2, 1971, 46/11,124, 46/11,125; Mar. 3, 1971, 46/11,408,

Int. G01n 27/46 US. Cl. 204-195 M 7 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION The invention relates to a device for measuring an activity of lead ions and more particularly to a device comprising a selective electrode responsive to the activity of lead ions and a reference electrode.

Lead ion activity can be determined by several methods such as chelatometric titration, spectrophotography and polarography. However, these methods generally require troublesome pretreatment for the sample before the measurement of lead ions.

It is desirable for chemical industry to have a device for measuring the activity of lead ions in a solution without any troublesome pretreatment similar to that of a pH glass electrode for measuring the pH value of solution without any pretreatment of the solution to be tested.

An object of this invention is to provide a device for measuring directly the activity of lead ions in a solution.

A further object of this invention is to provide such a measuring device characterized by a high sensitivity to lead ions.

Another object of this invention is to provide a lead ion measuring device characterized by a high response to the lead ions.

These and other objects of this invention will be apparent upon consideration of the following detailed description taken together with accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a device for measuring lead ions in a solution in accordance with the invention; and

FIG. 2 is a cross sectional view of a disc for use in the device of FIG. 1.

A device for measuring an activity of lead ions according to the present invention comprises a selective electrode and a reference electrode immersed in a solution containing lead ions', whereby only another surface contacts with said solution. Said lead ion-selective electrode includes a disc which is in a batch composition comprising a combination of lead chalcogenide and at least one member selected from the group consisting of silver telluride and silver selenide, or in a batch composition comprising a combination of silver sulfide and at least one member selected from the group consisting of lead telluride and lead selenide. Said batch composition according to the present invention achieve a lead ion-selective electrode having a high sensitivity and a wide application range with pH value in a solution to be tested.

Referring to FIG. 1, reference character 10 designates, as a whole, a selective electrode which comprises a disc in a batch composition according to the present invention. Said lead 3 is enveloped by a sealed wire 4. A combination of said disc 1 and said lead 3 partly enveloped by said sealed wire 4 is enclosed in a housing 2 so that another surface of said disc 1 contacts with a solution 6. Said housing 2 is filled with an insulating resinous material 5. A reference electrode 7 partly immersed in said solution 6 is electrically connected to one terminal of a voltmeter 8 having a high impedance. Said lead 3 is electrically connected to another terminal of said voltmeter 8.

A variation in the logarithm of the activity of lead ions in said solution 6 has a substantially linear relation to the variation in the potential between said selective electrode 10 and said reference electrode 7, both being partly immersed in said solution 6. One can use any available and suitable electrode such as a saturated calomel electrode or a silver-silver chloride electrode as said reference electrode 7.

Said disc 1 is in a batch composition comprising a combination of 5-95 wt. percent of lead chalcogenide and 5-95 wt. percent of at least one member selected from the group consisting of silver telluride and silver selenide, or in a batch composition comprising a combination of 5-95 wt. percent of silver sulfide and 5-95 wt. percent of at least one member selected from the group consisting of lead telluride and lead selenide in accordance with the invention.

A batch composition comprising a combination of more than 95 wt. percent of lead chalcogenide and less than 5 wt. percent of silver chalcogenide results in a low sensitivity of resultant electrode. A batch composition comprising a combination of less than 5 wt. percent of lead chalcogenide and more than 95 wt. percent of silver chalcogenide results in a low sensitivity and a long response time of resultant electrode.

Lead chalcogenide referred to herein is defined as lead sulfide, lead selenide and lead telluride.

A batch composition referred to herein is defined as a composition of starting materials before heating.

A better result is obtained by using a batch composition wherein said silver sulfide includes at least one member selected from the group consisting of silver selenide and silver telluride, the weight ratio of said silver sulfide to said one member being in a range from 1 to 10. This batch composition results in a high sensitivity and a short response time of resultant electrode.

A more preferable batch composition comprises a combination consisting essentially of 10 to 30 wt. percent of lead telluride and 70 to wt. percent of silver sulfide.

A longer operation life can be obtained by providing said disc with a noble metal electrode such as gold, palladium or platinum electrode. Referring to FIG. 2 a disc 1 has a noble metal electrode 9 applied to one surface thereof. A lead 3 is electrically connected to said noble metal electrode 9 by any available and suitable method such as soldering. Said noble metal electrode 9 can be prepared by, for example, vacuum-depositing of a noble metal film or by applying an available commercially noble metal paint.

The disc for use in said selective electrode can be obtained by heating a pressed body of a mixture of a given batch composition in a non-oxidizing atmosphere in accordance with a conventional ceramic method.

A mixture of starting materials of a fine powder form in a given batch composition according to the present invention is mixed well in a dry method by any suitable and available equipment and is pressed into a disc in a desired form at a pressure of 100 to 20,000 kg./cm. The pressed disc is heated at a temperature of 100 to 600 C. for time period of 1 to 10 hours preferably in a non-oxidizing atmosphere, such as nitrogen or argon.

The device according to the invention can be reliably used at temperatures from to 95 C. The measured potential versus the logarithm of the activity of lead ions is substantially linear relation.

Many kinds of diverse ions such as sodium, potassium, calcium, magnesium, nickel, cobalt, aluminum, zinc, chloride, sulfate, nitrate and perchlorate ions are tolerated and may coexist during the measurement of the activity of the lead ions. However, cupric, ferric, silver, mercuric, iodide and sulfide ions should be removed from the solution to be measured.

Example 1 A mixture of 25 wt. percent of lead telluride and 75 wt. percent of silver sulfide is mixed well in a dry method and is pressed at a pressure of 10,000-20,000 kg./cm. into a disc 15 mm. diameter and having a 3 mm. thickness. The pressed disc is heated at 400 C. for 2 hours in purified nitrogen gas stream having a flow rate of 0.2 l./min. The sintered disc is polished, at both surfaces, with silicon carbide abrasive and then with diamond paste into a thickness of 2 mm. The polished disc is provided, at one surface, with a gold electrode which is obtained from Du Pont gold paint #8115. The polished disc is connected, at the gold electrode, to a lead partly enveloped by a sealed wire and is mounted in a housing of polyvinyl chloride resin. The housing is filled with epoxy resin so as to build a selective electrode as shown in FIG. 1. A combination of the selective electrode and a saturated calomel electrode as a reference electrode is immersed in an aqueous solution of pure lead nitrate at 25 C. The potential between the selective electrode and the calomel electrode is measured by a voltmeter for use in a pH meter.

Th device measures the activity of lead ions with a high sensitivity as shown in Table 1.

A device for measuring the activity of lead ions is prepared in a manner similar to that of Example 1. A disc of Example 2 includes lead sulfide and silver telluride. The preparation of the disc is similar to that of Example 1. The potential between the selective electrode and a calomel electrode in the aqueous solution of pure lead nitrate is measured with the same procedure described in Example 1. The device measures the activity of lead ions with a high sensitivity as shown in Table 2.

TABLE 2 Potential, mv.

Activity of lead ions, M 1:99 I 5:95 B 25:75 I 90:10 P

I Weight ratio of lead sulfide:silver telluride.

4 Example 3 The device for measuring the activity of lead ions is prepared in a manner similar to that of Example 1. A disc of Example 3 is in a composition of a mixture of the starting materials, lead selenide and silver sulfide. The preparation of the discis similar to that of Example 1. The potential between the selective electrode and a saturated calomel electrode in an aqueous solution of pure lead nitrate is measured by the same procedure described in Example 1. The device measures the activity of lead ions with a high sensitivity as shown in Table 3.

TABLE 3 Potential, mv.

Activity of lead ions, M 1:99 a 5:95 a 25:75 a 60:40 h :10

a Weight ratio of lead selenidezsilver sulfide.

Example 4 The device for measuring the activity of lead ions is prepared in a manner similar to that of Example 1. A disc of Example. 4 is in a composition of a mixture of the starting materials, lead telluride and silver selenide. The preparation of the disc is similar to that of Example 1. The potential between the selective electrode and a saturated calomel electrode in an aqueous solution of pure lead nitrate is measured by the same procedure described in Example 1. The device measures the activity of lead ions with a high sensitivity as shown in Table 4.

TABLE 4 Potential, mv.

Activity of lead ions, M 1:99 I 5:95 B 25:75 a 60:40 I 90:10

- Weight ratio of lead telluridezsilver selenide.

EXAMPLE 5 The device for measuring the activity of lead ions is prepared in a manner similar to that of Example 1. A disc of Example 5 is in a composition of a mixture of the starting materials, lead selenide and silver selenide. The preparation of the disc is similar to that of Example 1. The potential between the selective electrode and a saturated calomel electrode in an aqueous solution of pure lead nitrate is measured by the same procedure described in Example 1. The device measures the activity of lead ions with a high sensitivity as shown in Table 5.

A device for measuring the activity of lead ions is prepared in. a manner similar to that. 9i Example 1. A disc of Example 6 includes 25 wt. percent of lead telluride, 35 wt. percent of silver selenide and 40 wt. percent of silver sulfide. The preparation of the disc is similar to that of Example 1. The potential between the selective electrode and a saturated calomel electrode in an aqueous solution of pure lead nitrate is measured with the same procedure described in Example 1. The device measures the activity of lead ions with a high sensitivity as shown in Table 6.

EXAMPLE 7 A device for measuring the activity of lead ions is prepared in a manner similar to that of Example 1. A disc of Example 7 includes 15 wt. percent of lead sulfide, 15% of lead telluride, 50% of silver sulfide and 20% of silver selenide as the starting materials. The preparation of the disc is similar to that of Example 1. The potential between the selective electrode and a saturated calomel electrode in an aqueous solution of lead nitrate is measured with the same procedure described in Example 1. The device measures the activity of lead ions with a high sensitivity as shown in Table 7.

EXAMPLE 8 A device for measuring the activity of lead ions is prepared in a manner similar to that of Example 1. A disc of Example 8 includes 10 wt. percent of lead selenide, of lead telluride and 75% of silver sulfide as the starting materials. The preparation of the disc is similar to that of Example 1. The potential between the selective electrode and a saturated calomel electrode in an aqueous solution of lead nitrate is measured with the same procedure described in Example 1. The device measures the activity of lead ions with a high sensitivity as shown in Table 8.

TABLE 8 Activity of lead ions, M: Potential mv. 1O -20 10- ---47 10- What is claimed is:

1. A device for measuring the activity of lead ions, comprising a selective electrode and a reference electrode which are coupled through a potential measuring apparatus, said selective electrode including a disc which is a batch composition comprises a combination of lead chalcogenide and at least one member selected from the group consisting of silver telluride and silver selenide.

2. A device for measuring the activity of lead ions as defined in claim 1, wherein said batch composition comprises a combination of 5-60 Wt. percent of lead chalcogenide and 40-95 wt. percent of at least one member selected from the group consisting of silver telluride and silver selenide.

3. A device for measuring the activity of lead ions as defined in claim 2, wherein said lead chalcogenide is at least one member selected from the group consisting of lead sulfide, lead selenide and lead telluride.

4. A device for measuring the activity of lead ions, comprising a selective electrode and a reference electrode which are coupled through a potential measuring apparatus, said selective electrode including a disc which in a batch composition comprises a combination of silver chalcogenide and at least one member selected from the group consisting of lead selenide and lead telluride.

5. A device for measuring the activity of lead ions as defined in claim 4, wherein said batch composition comprises a combination of 40-95 wt. percent of silver chalcogenide and 5-60 wt. percent of at least one member selected from the group consisting of lead telluride and lead selenide.

6. A device for measuring the activity of lead ions as defined in claim 4, wherein said silver chalcogenide is at least one member selected from the group consisting of 'silver sulfide, silver selenide and silver telluride.

7. A device for measuring the activity of lead ions as defined in claim 4, wherein said combination is of 10-30 wt. percent of lead telluride and 70-90 wt. percent of silver sulfide.

References Cited UNITED STATES PATENTS 3,591,464 7/1971 Frant et al 204-1 T 3,669,862 6/1972 Hirata et al. 204l95 M TA-HSUNG TUNG, Primary Examiner US. Cl. X.R. 2041 T 

